Technical Field
This invention relates to a method for manufacturing and applying a friction reducer with active components based on water soluble surfactants, to reduce friction of heavy and extra-heavy crude oil.
State of the Art
Heavy oil presents production challenges due to its high density and generally viscous nature. In the general equation for pipeline flow Δp is dependent on density and friction factor:
                              Δ          ⁢                                          ⁢          p                =                              1            2                    ⁢          f          ⁢                      ρ            d                    ⁢                      Lu            2                                              (        1        )            Where:Δp=differential pressure in the pipe;f=friction factor of the fluid;ρ=density of the fluid;d=pipe diameter;L=length of pipe, andu=velocity of the fluid flowing through the pipe.
While the density of heavy oils varies within about ±10% of the average, the friction factor may vary by several orders of magnitude. The friction factor is dependent on both density and viscosity, but the relationship changes as the flow regime changes.
The Reynold's number is used to determine whether the flow in a pipeline is laminar, transitional or turbulent. The Reynolds number Re is given by:
                    Re        =                              ρ            ⁢                                                  ⁢            du                    μ                                    (        2        )            Where:ρ=density of the fluid;d=pipe diameter;u=flow velocity, andμ=fluid viscosity.
At high viscosity levels, the pressure drop in pipelines may become economically prohibitive, or even prevent flow altogether. Pressure drop is the difference between the pressures at two different points in the pipeline. Pressure drop occurs when frictional forces, caused by the resistance to flow, act on the crude oil as it flows through the pipeline. Pressure drop increases proportionally to the frictional shear forces within the pipeline. High crude oil viscosities result in a large pressure drop. The main factors contributing to fluid flow resistance, viscosity and frictional forces result in increased pumping energy. In fact, one of the most important issues in the heavy oil production side is represented by the high cost of pumping energy required.
The viscoelastic rheology of heavy oil increases the friction forces in the pipeline, yielding an inefficient use of the energy used to pump the heavy oil through the pipeline, which worsens when temperature becomes lower.
Conventional methods for reducing high values of pressure drop in the pipeline include partial upgrading of the oil, dilution of the oil, heating of the oil, and usage of high molecular weight polymers as an additive to the oil. These methods enable changes in the original properties of the heavy or extra-heavy crude oil, yielding lower viscosity and friction reduction. However, these methods are economically infeasible and not totally efficient.
High molecular weight polymers are referred to as drag reducer additives (DRA). These additives are usually long chain and high molecular weight polymers added to the flow in turbulent regimens to enable a reduction of friction forces.
DRAs inhibit the formation of turbulent burst and prevent turbulence from being formed in the pipeline oil, or at least reduce the degree of turbulence, and in turn, reduce the drag or pressure loss. The drag reducer additive polymers are believed to stretch in the oil flow, absorbing the energy in the streak, thereby preventing turbulent burst in the oil. In general, the higher the degree of turbulence of the fluid in the pipeline, the more necessary the drag reducing additives. However, one limitation for the DRA polymers is that degradation can occur during the flow. Because of the pressure and temperature on the polymers, it is easier to break them down. Because of this, the drag reducing agent usually is re-injected after pumps and turns, where the pressure and temperature drops can be extra high.
Currently, producing and transporting heavy crude often requires the addition of diluting agents or diluents, such as, light crude, diesel, aromatic solvents, naphtha, and/or gasoline. These diluents behave as viscosity reducers or DRAs, albeit their high costs and volume required (e.g. 1 barrel of diluent per 3 barrels of heavy oil) increases the cost of the oil. Therefore, there is a need to find new additives to minimize diluent costs.
Accordingly, what is needed is a method of reducing friction in heavy and extra heavy crude oil, which yields savings by reducing the consumption of pumping energy and increasing the oil production rate.